1. Field of the Invention
The present invention generally relates to a vibrating gyroscope and an electronic unit including the same. More particularly, the present invention relates to a vibrating gyroscope for use in, for example, a hand-shaking correction device for use in, for example, an automobile navigation system or a video camera, and to an electronic unit including such a vibrating gyroscope.
2. Description of the Related Art
A gyroscope is used for, for example, a hand-shaking correction device for use in an automobile navigation system or a video camera. One type of such a gyroscope is a vibrating gyroscope for detecting the angular velocity applied to a vibrator by detecting distortion of a bar-shaped bending-vibrating-type vibrator caused by the Coriolis force. In the vibrating gyroscope, it is necessary to support the vibrator without interfering with the vibration of the vibrator. Japanese Unexamined Patent Application Publication No. 11-125526 discloses a structure for supporting a vibrator.
In the vibrating gyroscope disclosed in this publication, a bar-shaped vibrator having two main surfaces (first and second main surfaces) includes a pair of supporting members fixed to electrodes disposed on the first and second main surfaces, respectively, in the vicinity of two node points of double-end-free bending vibration generated by driving. The supporting members extend from the first and second main surfaces of the vibrator in the widthwise direction of the vibrator. A bending portion having a component in the longitudinal direction of the vibrator is also provided between the portion of the supporting member fixed to the electrode and the end of the supporting member.
Thus, the supporting members are arranged to avoid seriously interfering with the vibration of the vibrator, and leakage of the vibration of the vibrator to the exterior is also minimal.
However, the vibrating gyroscope disclosed in the above-identified publication suffers from the following problems. The vibration nodes of the vibrator are positioned within the vibrator. On the other hand, the supporting members are fixed on the first and second main surfaces of the vibrator, and the portions other than the portions fixed to the first and second main surfaces are also positioned in the plane extending from the first and second main surfaces. This is different from the ideal arrangement of supporting members for supporting the vibrator at the node points. Thus, the vibration and the deformation of the supporting members caused by the vibration of the vibrator become relatively large, and the vibration of the vibrator leaks to the exterior via the supporting members. This makes the vibration unstable, thereby decreasing the detection precision of the angular velocity.
FIG. 6 illustrates the change in resonant frequency of the vibrator in the vibrating gyroscope disclosed in the above-described publication before and after the supporting members are attached. In FIG. 6, the vertical resonant frequency indicates the resonant frequency in the vibration in the thickness direction of the vibrator, i.e., the resonant frequency in the vibration caused by driving. The horizontal resonant frequency indicates the resonant frequency in the vibration in the widthwise direction of the vibrator, i.e., the resonant frequency in the vibration caused by the Coriolis force. The detuning frequency indicates the difference between the vertical resonant frequency and the horizontal resonant frequency.
FIG. 6 shows that there is a great difference between the change in vertical resonant frequency and the change in horizontal resonant frequency before and after the supporting members are attached, and thus, the detuning frequency is considerably changed. The vertical resonant frequency and the horizontal resonant frequency of the vibrator are changed by a restraining force that is generated due to the attachment of the supporting members. Such a restraining force is canceled by external disturbances, such as mechanical impact or thermal impact, and the vertical frequency and the horizontal frequency may return to the original frequencies. Accordingly, the detuning frequency may also return to the original frequency, i.e., the detuning frequency is changed. In the vibrating gyroscope, the change in detuning frequency influences the sensitivity for detecting the Coriolis force, the temperature characteristics, and the response characteristics. Thus, if the detuning frequency is changed for some reason, for example, by attaching supporting members after completion of the vibrating gyroscope, the sensitivity, the temperature characteristics, and the response characteristics are disadvantageously changed.
In order to solve the problems described above, preferred embodiments of the present invention provide a vibrating gyroscope which achieves minimal interference with the vibration of a vibrator and which does not experience a change in the sensitivity, the temperature characteristics, and the response characteristics over time, and also the preferred embodiments provide an electronic unit including such a novel vibrating gyroscope.
According to a preferred embodiment of the present invention, a vibrating gyroscope includes a bar-shaped vibrator for performing double-end-free bending vibration in a thickness direction and in a widthwise direction thereof, and supporting members arranged to sandwich the vicinities of two node points of the vibrator from both sides of the vibrator in the thickness direction. The supporting members are arranged such that they extend from positions at which they are fixed to the vibrator in the widthwise direction of the vibrator, and also include intermediate portions positioned substantially on a plane which is parallel to the widthwise direction and the longitudinal direction of the vibrator and which passes through the approximate center of the vibrator in the thickness direction.
The supporting members may extend to both sides in the widthwise direction of the vibrator so as to define the intermediate portions.
Also, the supporting member may include at least one bending portion at the position of the intermediate portion.
The bending portions of the supporting members positioned on both sides of the vibrator in the thickness direction in the vicinity of each of the node points may bend in the opposite directions with respect to the longitudinal direction of the vibrator.
The bending portions of the supporting members positioned on one side of the vibrator in the thickness direction in the vicinities of the two node points may bend in the opposite directions with respect to the longitudinal direction of the vibrator, and the bending portions of the supporting members positioned on the other side of the vibrator in the thickness direction in the vicinities of the two node points may bend in the opposite directions with respect to the longitudinal direction of the vibrator.
The supporting members may be preferably made of a conductive material, and may be electrically and mechanically connected to electrodes disposed on the vibrator.
The vibrator may include a first main surface and a second main surface, and the electrodes may be located on the first main surface and the second main surface.
The vibrating gyroscope may further include a supporting base. In this case, the supporting members may be bent toward one side of the vibrator in the thickness direction and may be fixed on the supporting base, thereby retaining the vibrator in a space above the supporting base.
Alternatively, the vibrating gyroscope may further include an opened-box-type base having side walls and having a hollowed out portion at the center thereof. In this case, the ends of the supporting members may be fixed to the opened-box-type base, thereby retaining the vibrator in the hollowed out portion of the opened-box-type base.
According to the vibrating gyroscope of various preferred embodiments of the present invention, the vibrator can be supported by the supporting members at the node axes. Accordingly, leakage of the vibration to the exterior is reliably prevented, and the vibration becomes stable, thereby improving the detection precision of the angular velocity. Additionally, the sensitivity for detecting the Coriolis force, the temperature characteristics, and the response characteristics do not change in any meaningful way over time.
An electronic unit according to a preferred embodiment of the present invention includes a vibrating gyroscope according to the preferred embodiments described above.
According to the electronic unit of a preferred embodiment of the present invention, the performance of the electronic unit is greatly improved by using the vibrating gyroscope of the present invention.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.